PropertyArrayView.h

#pragma once
 
#include <CesiumGltf/PropertyType.h>
#include <CesiumGltf/getOffsetFromOffsetsBuffer.h>
#include <CesiumUtility/SpanHelper.h>
 
#include <cstddef>
#include <cstring>
#include <span>
#include <vector>
 
namespace CesiumGltf {

template <typename ElementType> class PropertyArrayView {
public:
  PropertyArrayView() : _values{} {}

  PropertyArrayView(const std::span<const std::byte>& buffer) noexcept
      : _values{CesiumUtility::reintepretCastSpan<const ElementType>(buffer)} {}

  const ElementType& operator[](int64_t index) const noexcept {
    return this->_values[static_cast<size_t>(index)];
  }

  int64_t size() const noexcept {
    return static_cast<int64_t>(this->_values.size());
  }

  auto begin() { return this->_values.begin(); }
  auto end() { return this->_values.end(); }
  auto begin() const { return this->_values.begin(); }
  auto end() const { return this->_values.end(); }
 
private:
  std::span<const ElementType> _values;
};

template <typename ElementType> class PropertyArrayCopy {
public:
  PropertyArrayCopy() : _storage{}, _view() {}

  PropertyArrayCopy(const std::vector<ElementType>& values) noexcept
      : _storage(), _view() {
    size_t numberOfElements = values.size();
    size_t sizeInBytes = numberOfElements * sizeof(ElementType);
    this->_storage.resize(sizeInBytes);
    std::memcpy(
        this->_storage.data(),
        reinterpret_cast<const std::byte*>(values.data()),
        sizeInBytes);
    // NOLINTNEXTLINE(cppcoreguidelines-prefer-member-initializer)
    this->_view = PropertyArrayView<ElementType>(this->_storage);
  }

  PropertyArrayCopy(PropertyArrayCopy&&) = default;
  PropertyArrayCopy& operator=(PropertyArrayCopy&&) = default;

  PropertyArrayCopy(std::vector<std::byte>&& buffer) noexcept
      : _storage(std::move(buffer)), _view(this->_storage) {}

  PropertyArrayCopy(const PropertyArrayCopy& rhs)
      : _storage(rhs._storage), _view(this->_storage) {}

  PropertyArrayCopy& operator=(const PropertyArrayCopy& rhs) {
    this->_storage = rhs._storage;
    this->_view = PropertyArrayView<ElementType>(this->_storage);
    return *this;
  }

  const ElementType& operator[](int64_t index) const noexcept {
    return this->_view[index];
  }

  int64_t size() const noexcept { return this->_view.size(); }

  auto begin() { return this->_view.begin(); }
  auto end() { return this->_view.end(); }
  auto begin() const { return this->_view.begin(); }
  auto end() const { return this->_view.end(); }

  const PropertyArrayView<ElementType>& view() const { return this->_view; }

  PropertyArrayView<ElementType>
  toViewAndExternalBuffer(std::vector<std::byte>& outBuffer) && {
    outBuffer = std::move(this->_storage);
    PropertyArrayView<ElementType> result = std::move(this->_view);
    this->_view = PropertyArrayView<ElementType>();
    return result;
  }
 
private:
  std::vector<std::byte> _storage;
  PropertyArrayView<ElementType> _view;
};

template <> class PropertyArrayView<bool> {
public:
  PropertyArrayView() : _values{}, _bitOffset{0}, _size{0} {}

  PropertyArrayView(
      const std::span<const std::byte>& buffer,
      int64_t bitOffset,
      int64_t size) noexcept
      : _values{buffer}, _bitOffset{bitOffset}, _size{size} {}

  bool operator[](int64_t index) const noexcept {
    index += _bitOffset;
    const int64_t byteIndex = index / 8;
    const int64_t bitIndex = index % 8;
    const int bitValue =
        static_cast<int>(_values[static_cast<size_t>(byteIndex)] >> bitIndex) &
        1;
    return bitValue == 1;
  }

  int64_t size() const noexcept { return _size; }
 
private:
  std::span<const std::byte> _values;
  int64_t _bitOffset;
  int64_t _size;
};

template <> class PropertyArrayCopy<bool> {
public:
  PropertyArrayCopy() : _storage{}, _view() {}

  PropertyArrayCopy(const std::vector<bool>& values) noexcept
      : _storage(), _view() {
    size_t numberOfElements = values.size();
    size_t sizeInBytes = (numberOfElements + 7) / 8;
    this->_storage.resize(sizeInBytes);
 
    for (size_t byteIndex = 0, valueIndex = 0; byteIndex < sizeInBytes;
         byteIndex++) {
      uint8_t byte = 0;
      for (size_t bitIndex = 0; bitIndex < 8 && valueIndex < numberOfElements;
           bitIndex++, valueIndex++) {
        uint8_t bit = uint8_t(values[valueIndex]);
        byte |= bit << bitIndex;
      }
      this->_storage[byteIndex] = std::byte(byte);
    }
 
    this->_view = PropertyArrayView<bool>(
        this->_storage,
        0,
        static_cast<int64_t>(numberOfElements));
  }

  PropertyArrayCopy(PropertyArrayCopy&&) = default;
  PropertyArrayCopy& operator=(PropertyArrayCopy&&) = default;

  PropertyArrayCopy(const PropertyArrayCopy& rhs)
      : _storage(rhs._storage), _view(this->_storage, 0, rhs.size()) {}

  PropertyArrayCopy& operator=(const PropertyArrayCopy& rhs) {
    this->_storage = rhs._storage;
    this->_view = PropertyArrayView<bool>(this->_storage, 0, rhs.size());
    return *this;
  }

  bool operator[](int64_t index) const noexcept { return this->_view[index]; }

  int64_t size() const noexcept { return this->_view.size(); }

  const PropertyArrayView<bool>& view() const { return this->_view; }

  PropertyArrayView<bool>
  toViewAndExternalBuffer(std::vector<std::byte>& outBuffer) && {
    outBuffer = std::move(this->_storage);
    PropertyArrayView<bool> result = std::move(this->_view);
    this->_view = PropertyArrayView<bool>();
    return result;
  }
 
private:
  std::vector<std::byte> _storage;
  PropertyArrayView<bool> _view;
};

template <> class PropertyArrayView<std::string_view> {
public:
  PropertyArrayView()
      : _values{},
        _stringOffsets{},
        _stringOffsetType{PropertyComponentType::None},
        _size{0} {}

  PropertyArrayView(
      const std::span<const std::byte>& values,
      const std::span<const std::byte>& stringOffsets,
      PropertyComponentType stringOffsetType,
      int64_t size) noexcept
      : _values{values},
        _stringOffsets{stringOffsets},
        _stringOffsetType{stringOffsetType},
        _size{size} {}

  std::string_view operator[](int64_t index) const noexcept {
    const size_t currentOffset = getOffsetFromOffsetsBuffer(
        static_cast<size_t>(index),
        _stringOffsets,
        _stringOffsetType);
    const size_t nextOffset = getOffsetFromOffsetsBuffer(
        static_cast<size_t>(index + 1),
        _stringOffsets,
        _stringOffsetType);
    return std::string_view(
        reinterpret_cast<const char*>(_values.data() + currentOffset),
        (nextOffset - currentOffset));
  }

  int64_t size() const noexcept { return _size; }
 
private:
  std::span<const std::byte> _values;
  std::span<const std::byte> _stringOffsets;
  PropertyComponentType _stringOffsetType;
  int64_t _size;
 
  friend class PropertyArrayCopy<std::string_view>;
};

template <> class PropertyArrayCopy<std::string_view> {
public:
  PropertyArrayCopy() : _storage{}, _view() {}

  PropertyArrayCopy(const std::vector<std::string>& values) noexcept
      : _storage(), _view() {
    size_t numberOfElements = values.size();
    size_t totalLength = 0;
    for (const std::string& value : values) {
      totalLength += value.size();
    }
 
    std::vector<std::byte> stringData(totalLength);
    std::vector<std::byte> offsetData;
 
    auto copyDataWithOffsetType = [&]<typename TOffsetType>() {
      offsetData.resize(sizeof(TOffsetType) * numberOfElements + 1);
      TOffsetType* pOffset = reinterpret_cast<TOffsetType*>(offsetData.data());
 
      TOffsetType writeOffset = 0;
      for (size_t i = 0; i < numberOfElements; i++) {
        const std::string& value = values[i];
        std::memcpy(
            stringData.data() + writeOffset,
            value.data(),
            value.size());
 
        *pOffset = writeOffset;
        writeOffset += TOffsetType(value.size());
        pOffset++;
      }
 
      *pOffset = writeOffset;
    };
 
    PropertyComponentType offsetType;
    if (totalLength < size_t(std::numeric_limits<uint8_t>::max())) {
      offsetType = PropertyComponentType::Uint8;
      copyDataWithOffsetType.template operator()<uint8_t>();
    } else if (totalLength < size_t(std::numeric_limits<uint16_t>::max())) {
      offsetType = PropertyComponentType::Uint16;
      copyDataWithOffsetType.template operator()<uint16_t>();
    } else if (totalLength < size_t(std::numeric_limits<uint32_t>::max())) {
      offsetType = PropertyComponentType::Uint32;
      copyDataWithOffsetType.template operator()<uint32_t>();
    } else {
      offsetType = PropertyComponentType::Uint64;
      copyDataWithOffsetType.template operator()<uint64_t>();
    }
 
    this->_storage.resize(stringData.size() + offsetData.size());
    std::memcpy(this->_storage.data(), stringData.data(), stringData.size());
    std::memcpy(
        this->_storage.data() + static_cast<int32_t>(stringData.size()),
        offsetData.data(),
        offsetData.size());
 
    this->_view = PropertyArrayView<std::string_view>(
        std::span<const std::byte>(this->_storage.data(), stringData.size()),
        std::span<const std::byte>(
            this->_storage.data() + static_cast<int32_t>(stringData.size()),
            offsetData.size()),
        offsetType,
        static_cast<int64_t>(numberOfElements));
  }

  PropertyArrayCopy(PropertyArrayCopy&&) = default;
  PropertyArrayCopy& operator=(PropertyArrayCopy&&) = default;

  PropertyArrayCopy(const PropertyArrayCopy& rhs)
      : _storage(rhs._storage), _view() {
    // Reconstruct spans so they point to this copy's data.
    size_t valueSpanSize = rhs._view._values.size();
    size_t offsetSpanSize = this->_storage.size() - valueSpanSize;
    this->_view = PropertyArrayView<std::string_view>(
        std::span<const std::byte>(this->_storage.data(), valueSpanSize),
        std::span<const std::byte>(
            this->_storage.data() + static_cast<int32_t>(valueSpanSize),
            offsetSpanSize),
        rhs._view._stringOffsetType,
        rhs._view.size());
  }

  PropertyArrayCopy& operator=(const PropertyArrayCopy& rhs) {
    this->_storage = rhs._storage;
    // Reconstruct spans so they point to this copy's data.
    size_t valueSpanSize = rhs._view._values.size();
    size_t offsetSpanSize = this->_storage.size() - valueSpanSize;
    this->_view = PropertyArrayView<std::string_view>(
        std::span<const std::byte>(this->_storage.data(), valueSpanSize),
        std::span<const std::byte>(
            this->_storage.data() + static_cast<int32_t>(valueSpanSize),
            offsetSpanSize),
        rhs._view._stringOffsetType,
        rhs._view.size());
    return *this;
  }

  std::string_view operator[](int64_t index) const noexcept {
    return this->_view[index];
  }

  int64_t size() const noexcept { return this->_view.size(); }

  const PropertyArrayView<std::string_view>& view() const {
    return this->_view;
  }

  PropertyArrayView<std::string_view>
  toViewAndExternalBuffer(std::vector<std::byte>& outBuffer) && {
    outBuffer = std::move(this->_storage);
    // Moving a std::vector should not affect the memory addresses of the heap
    // data, so the spans are still valid.
    PropertyArrayView<std::string_view> result = std::move(this->_view);
    this->_view = PropertyArrayView<std::string_view>();
    return result;
  }
 
private:
  std::vector<std::byte> _storage;
  PropertyArrayView<std::string_view> _view;
};

template <typename T>
bool operator==(
    const PropertyArrayView<T>& lhs,
    const PropertyArrayView<T>& rhs) {
  int64_t size = lhs.size();
  if (size != rhs.size()) {
    return false;
  }
 
  for (int64_t i = 0; i < size; ++i) {
    if (lhs[i] != rhs[i]) {
      return false;
    }
  }
 
  return true;
}

template <typename T>
bool operator==(
    const PropertyArrayView<T>& lhs,
    const PropertyArrayCopy<T>& rhs) {
  return lhs == PropertyArrayView(rhs);
}

template <typename T>
bool operator==(
    const PropertyArrayCopy<T>& lhs,
    const PropertyArrayView<T>& rhs) {
  return lhs.view() == rhs;
}

template <typename T>
bool operator==(
    const PropertyArrayCopy<T>& lhs,
    const PropertyArrayCopy<T>& rhs) {
  return lhs.view() == rhs.view();
}

template <typename T>
bool operator!=(
    const PropertyArrayView<T>& lhs,
    const PropertyArrayView<T>& rhs) {
  return !(lhs == rhs);
}

template <typename T>
bool operator!=(
    const PropertyArrayView<T>& lhs,
    const PropertyArrayCopy<T>& rhs) {
  return !(lhs == rhs);
}

template <typename T>
bool operator!=(
    const PropertyArrayCopy<T>& lhs,
    const PropertyArrayView<T>& rhs) {
  return !(lhs == rhs);
}

template <typename T>
bool operator!=(
    const PropertyArrayCopy<T>& lhs,
    const PropertyArrayCopy<T>& rhs) {
  return !(lhs == rhs);
}
 
} // namespace CesiumGltf